The use of heat exchangers is known in the prior art.
For example, U.S. Pat. No. 574,157 (Ljungstrom) describes a heat exchanger, wherein each single flow path (chamber) for one of the fluids is formed from a single sheet, which has been impressed with diagonal corrugations then folded over and sealed. This design is inherently a cross flow heat exchanger with the direction of flow of one fluid is at right angles to the direction of flow of the other fluid. The construction cannot be used for parallel flow heat exchanger. Structural support within the bundle is obtained by the crossing of the corrugations. The passageways formed have cross flow perpendicular to the direction of folding or rolling. Multiple flow passages for each fluid are created by stacking several individual chambers in a parallel arrangement. Accordingly, the corrugated surface for the Ljungstrom device is folded once then closed, i.e., the edges are sealed, to form a chamber. The chamber is then rolled or folded to form the passages for the second fluid. By contrast, in accordance with the present invention, as will be discussed later, the corrugated surface is folded multiple times to form multiple adjacent passages for the two fluids. The sheet is never closed, i.e., the edges are not sealed. There is no further folding required or stacking of several individual chambers. The Ljungstrom device is inherently a cross flow heat exchanger and the present invention is inherently a parallel flow heat exchanger. Even though FIGS. 15 and 16 of the Ljungstrom patent show a cylindrical pressure vessel providing structural support, there does not appear to be any structural support shown for the interior of the coiled chambers. Furthermore, the folded edges of the chambers may not be supported as the support would prevent flow of the second fluid. Thus, the Ljungstrom device may not withstand high differential pressure or high absolute pressure of the two fluids. The headers for introduction of fluid are not equivalent or equal to the headers for fluid as they are in the heat exchanger of the present invention.
U.S. Pat. No. 3,640,340 (Leonard et al.) discloses a heat exchange surface formed from a single sheet by folding with flow parallel to the folds and ports at the periphery of the bundle to introduce flow onto and remove the flow from the bundle. It shows embedded side and end seals and a flow seal function built into the manifolds. However, unlike the present invention, as will be discussed later, the Leonard et al. device includes no diagonal corrugations, which provide structural rigidity and flow turbulence. There is no separate cylindrical pressure vessel, i.e., the configuration is not optimum for resistance to pressure forces. The seals do not contribute to the carrying of structural loads due to pressure. The potting for the embedded seals is not further structurally supported by the pressure vessel and the headers are not inherently defined by the space between the pressure vessel, the bundle and the back of the flow seal and the embedded end seal.
U.S. Pat. No. 3,759,322 (Nasser et al.) discloses a heat exchanger whereby the passages of the heat exchanger are defined by stacks of identical diagonally corrugated and lipped plates oriented in alternating fashion, such that the lips can be welded together. Inside the passages are stacks of a differently sized plate utilized for structural support (through crossed corrugations). The housing is rectangular with partitioned inlets and outlets for fluids. The Nasser et al. heat exchanger is constructed from multiple plates welded together to form separate passages whereas the present invention is constructed from a single sheet. In the Nasser et al. device, the passages contain a smaller auxiliary corrugated plate for structural support and thermal storage whereas the present invention does not use auxiliary plates nor attempt to use thermal storage. The Nasser et al. device lacks embedded seals or flow seals, which also provide structural support between the bundle and the vessel, and which help to define port areas.
U.S. Pat. No. 2,288,061 (Arnold) discloses an oil cooler/heat exchanger having a core for the cross flow heat exchanger that is comprised of a stack of formed, corrugated plates, which are assembled in a frame to create cross flow passages and barriers to commingling of the two fluids. The core is dip brazed or soldered to obtain fluid seals and structural strength. The soldering joins the faying surfaces of nesting corrugations and the crossed apices of the corrugations. Among other things, one difference between the Arnold device and the present invention is the manifold. In the Arnold device, there is a cross flow and not parallel flow. In the Arnold device, the corrugations are not diagonally disposed relative to the flow. Instead, the corrugations of one plate are in line with the flow and the corrugations of the adjacent plate lie across the direction of flow. This is a disadvantage as the flow path is not of constant area, but varies between full area and half area. This promotes heat exchanges at the expense of relatively much greater pressure drop. There are no embedded seals, or seal materials as part of the load path in the Arnold device and the passages are not defined by folding of a single sheet as is the case with the heat exchanger of the present invention.
U.S. Pat. No. 4,099,928 (Norback) discloses a cross flow heat exchanger constructed of a stack of diagonally corrugated, formed sheets with displaced edges, which form sealing surfaces. The orientation of adjacent sheets in the stack is adjusted to form adjacent sealed passages for fluids (1) and (2). The edges, which form sealing surfaces, are sealed by immersion in a sealer or by hemming (folding). A special corner seal serves to prevent commingling of the fluids at corners of the exchanger. The Norback system utilizes a cross flow rather than a parallel flow, as does the present invention, as will be described later. The Norback system also utilizes a stack of separate plates, not folded from a single sheet and the seals are not embedded seals.
U.S. Pat. No. 3,734,177 (Bellovary, et al.) discloses a parallel flow heat exchanger with adjacent passages defined by a non-corrugated sheet, which has been accordion folded. The pressure vessel is rectangular in shape and is shaped to define the flow ports. Longitudinal edges of the folded core are joined to two pressure vessel halves by a folded, soldered seam. The ends are sealed by two separate fingered plates each, which are sealed and joined by soldering or brazing. Turbulence is promoted and heat transfer increased by the addition of turbulator fins (separately formed sheets) into passageways. Some of the differences between the Bellovary et al. device and the present invention include: a heat exchange surface that is not corrugated, but is rather plain (which does not promote heat transfer which normally is improved by separate `turbulator` elements placed within the folds); the Bellovary et al. device seals are all flow-to-outside. The primary goal of the Bellovary et al. device construction is to make seals accessible for brazing and visible for inspection. In contrast, some of the heat exchanger embodiments of the present invention have embedded flow-to-flow seals (the flow-to-outside sealing is accomplished by a separate pressure vessel). The Bellovary et al. device pressure containment means is rectangular with longitudinal seams whereas the present invention pressure containment means is a separate cylindrical pressure vessel (the optimum shape). In the Bellovary et al. device there are no seals in the path from the heat transfer surface to the pressure containment means and the device will not support itself structurally.
U.S. Pat. No. 3,372,743 (Pall et al.) discloses a heat exchanger in which the primary heat exchange surface is impressed with longitudinal (not diagonal) corrugations. The surface is then folded. Corrugated separator plates are placed between the pleats, to space them apart, so that fluid can enter for the purpose of heat exchange. The flow arrangement is parallel flow. Structural strength is achieved by heavy pressure containing walls or by brazing together the crossed corrugations of the separator plates. Some of the differences between the present invention and the Pall et al. device are that the latter device's corrugations create individual passages (even the `cross corrugations`), which extend the full length of the heat transfer surface. In contrast, in the heat exchanger of the present invention, the diagonal corrugations do not extend full length of the surface and, in fact, this is not desirable. Furthermore, the Pall et al. device's corrugated, convoluted surface must be spaced apart by a separate corrugated separator plate to permit entry of fluid into the flow passages. Or, if the separator plates are smooth, a separately formed dimple (not part of the corrugation) must be impressed into the main surface to permit flow across the corrugations and into the bundle. The seals are not embedded as in the present heat exchanger. Seals are fluid-to-outside, not fluid-to-fluid as in the present invention.
Seals are part of the load path to the pressure vessel in one embodiment of the heat exchanger of the present invention and they are not in any of the following patents; the housings contain the flow distribution means. In contrast, in the present invention, in one embodiment, flow distribution means is defined by the periphery of the bundle, the cylindrical housing and the seals.
U.S. Pat. No. 817,490 (Jarvis) discloses an exchanger comprising of stacked, diagonally corrugated plates, flow entry through holes in the plates and a frame for clamping the plates.
U.S. Pat. No. 799,621 (Brewtnall) discloses an exchanger comprised of separate plates, diagonally corrugated and special inlet and outlet means for cross flow heat exchange.
U.S. Pat. No. 4,460,388 (Fukami et al.) discloses an exchanger comprised of a convoluted (folded) main surface (without corrugations). The walls of the main surface are spaced apart by separate spacer places, formed with corrugations, which serve as flow guides in the space between the folds.
British Patent 320,279 has a folded exchanger with an enhancement by corrugations and means for creating multiple separate flow plates and has a rectangular pressure vessel.
Japanese Patent 6-19408 has a folded exchanger surface with no corrugations and is not similar to the present invention.
It should be noted that in the distillation art, U.S. Pat. No. 5,700,403 (Billingham et al.) discloses a distillation column utilizing a packing element which reduces wall flow by varying corrugated sheet lengths. By varying the lengths of the corrugated sheet lengths to minimize the gap between the packing element and the column wall, any wall flow is driven back in towards the packing element. U.S. Pat. No. 5,224,351 (Jeannot et al.) discloses an air distillating column that utilizes a distributor element having individual linings with different lengths that span the circular perimeter of the interior of the column. However, among other things, neither of these references teach or suggest the utilization of a single sheet for transferring flow loads into the pressure vessel housing, as in the present invention.
Thus, there remains a need for a low cost heat exchanger that can accomplish heat transfer in an efficient manner between two flowing media while simultaneously transferring the pressure loads of the two flowing media to the pressure vessel walls.